Measure the inside of the shower floor to determine the width and the depth of your teak floor.
Cut 1-by 2-inch slats of teak into sections as long as the shorter measurement of your shower floor, less 1-1/2 inches for the end trim, with a table saw. To figure out how many to cut, divide the measurement of the floor by 1.5 to determine the number of 1-inch slats set 1/2-inch apart.
Lay out strips of double-sided carpet tape, 6 inches apart over the surface of a work area as large as the shower floor. Set the slats on the tape 1/2-inch apart.
Cut two end sections of teak trim that measure 1/2-inch by 2 inches as long as the longer measurement of your shower floor. Hold the trim against the ends of the slats.
Drill two pilot holes on each of the ends to match up with the slats and screw them in place with 2-inch galvanized wood screws.
Drill the rest of the pilot holes though the trim and into the slats, two for each slat, and screw them into place. Repeat for the second side.
Lift the wood from the tape and set it on your shower floor.